Project 1: Acoustic Plus Electric Hearing Preservation of residual acoustic hearing during cochlear implantation has become an important improvement in the performance of cochlear implants. Not only does it improve the performance of implants (particularly for noisy, real-world listening conditions) but also allows the treatment of patients with severe high-frequency hearing loss, who have substantial low-frequency hearing. This project proposes to continue this work on combining acoustic plus electric (A+E) hearing. In addition to the overall goal of improving patient care for hearing loss, several unique research opportunities arise from this work. The first opportunity arises because of the new population of patients that will be implanted with these A+E devices. Never before have patients with such high levels of pre-operative residual hearing been implanted in such a large- scale project. We are at the same time seeing levels of performance for the transmission of speech through the short electrode that are surprising in light of the previous literature. This will allow us to re-examine some of the commonly held beliefs about the limitations of electric stimulation due to channel interaction. The second opportunity arises because the short-electrode Hybrid implant assigns low- and mid-frequency speech bands to extreme basal locations in the cochlea. Thus we have a unique opportunity to study the effects of remapping, neural plasticity, and adaptation to highly-distorted place-frequency maps in the cochlea.